Space Radiation and Its Biological Effects

Galactic cosmic rays (GCR) and solar cosmic radiation (SCR) are the primary sources of the radiation field in space. Whereas the GCR component comprises all particles from protons to heavy ions with energies up to 10¹¹ GeV, the SCR component ejected in solar energetic particle (SEP) events consists mostly of protons, with a small percentage of heavy ions with energies up to several GeV. Fluxes of GCR particles are very low, around some particles cm^-2 s^-1; fluxes of solar protons may reach to 10¹⁰ particles cm^-2 released over several hours. GCR expose biological systems and humans to quite low mean dose rates not leading to acute radiation effects, but the exposure causes an additional risk of carcinogenesis, degenerative tissue effects, damages to the central nervous system and accelerated aging. Exposures to SEP also contribute to the listed risks, but in addition may cause acute effects, like performance degradation, acute radiation sickness or even death. To prevent exposures due to solar particles spacecraft can be equipped with shelters, but shielding is not effective against GCR. While the effects of high doses are relatively well investigated and reasonably understood, the biological effects caused by heavy ions are poorly understood. Mitigation of the effects of heavy ions is one of the most important challenges to be solved for the exploration of the solar system. This book contribution describes the radiation field, its biological effects and measures that are necessary to limit exposures in space missions to acceptable levels. Laser-driven ion acceleration can provide an advanced tool to study heavy ion effects in order to close gaps of knowledge.